Negative time calculation / formula

[cpisthedbb]

A B C D

05/12/2019 18:08 06/12/2019 05:50 11:41:43

06/12/2019 05:30 06/12/2019 05:5 -100,00 00:20:15



I wonder if someone could help with a formula I’m stuck on. I have the above table. Some of the times are negatives as per column C this is a time which has been deducted.



Is there a way of creating a column E which shows any with a ‘-100’ in C as negative time. Ie -00:20:15?

 

[mole999]

if you change the date system ( 1904 to 1900) or the other way round I can't recall then the formulas won't baulk at negative times. changing it will change all other displayed dates though by four years. Its stored as a whole number